The subject matter disclosed herein relates to ultrasonic testing, and more particularly, a method and system for calibrating an ultrasonic wedge and a probe.
Nondestructive testing devices can be used to inspect test objects to identify and analyze anomalies in the objects. Nondestructive testing allows an inspection technician to maneuver a probe at or near the surface of the test object in order to perform testing of both the object surface and underlying structure. Nondestructive testing can be particularly useful in some industries, e.g., aerospace, power generation, and oil and gas transport or refining, where inspection of test objects must take place without removal of the object from surrounding structures, and where hidden anomalies can be located that would otherwise not be identifiable through visual inspection.
One example of nondestructive testing is ultrasonic testing. When conducting ultrasonic testing, an ultrasonic pulse can be emitted from an ultrasonic transducer of a probe and passed through a test object. Electric pulses can be generated by a transmitter and can be fed to the probe where they can be transformed into ultrasonic pulses by ultrasonic transducers. One type of ultrasonic transducer—a phased array transducer—comprises a plurality of electrically and acoustically independent transducer elements that incorporate piezoelectric ceramics. During operation, an electrical waveform pulse is applied to the electrodes of the each of the phased array transducer elements of the probe causing a mechanical change in the condition of the piezoelectric ceramic and generating an acoustic wave that can be transmitted through a material such as a metal or plastic to which the probe is coupled. Conversely, when an acoustic wave reflected from the material under inspection contacts the surface of the piezoelectric ceramic of a phased array transducer element, it generates a voltage difference across the electrodes that is detected as a receive signal by signal processing electronics.
As the ultrasonic pulses pass through the object, various pulse reflections called echoes occur as the pulse interacts with internal structures within the test object and with the opposite side (back wall) of the test object. The echo signals can be displayed on the screen with echo amplitudes appearing as vertical traces and time of flight or distance as horizontal traces. By tracking the time difference between the transmission of the electrical pulse and the receipt of the electrical signal, and measuring the amplitude of the received acoustic wave, various characteristics of the material can be determined. Thus, for example, ultrasonic testing can be used to determine material thickness or the presence and size of anomalies within a given test object.
In some applications, e.g., when testing pipe welds, the probe can be mounted on an ultrasonic wedge that provides intermediary physical contact between the phased array transducer and the test object. In order to conduct the ultrasonic inspection of the test object, it is necessary to “set up” the inspection, including the calibration of the probe and ultrasonic wedge combination. This calibration procedure requires the ultrasonic technician to use the geometric and physical properties of the ultrasonic wedge and the phased array transducer of the probe to determine the ultrasonic signal acquisition width and the start and stop times for the ultrasonic signal gate during the calibration procedure.
The calibration procedure uses theoretical parameters of the particular phased array transducer of the probe and the ultrasonic wedge to make these determinations, which might vary from actual conditions. For example, if the phased array transducer has elements that are not operating properly or the ultrasonic wedge experienced wear that changes its geometry, the calibration, and therefore subsequent ultrasonic measurements, will be inaccurate based on the difference between the theoretical and the actual values of the parameters of the components. Given the complexity of these determinations made during the calibration procedure, the inspection technician conducting the calibration procedure must typically have a high level of ultrasonic expertise.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.